‘[Trump voters] don’t want to believe that they were stupid,’ says Robert Cialdini.

Despite the turmoil unleashed by his administration, Donald Trump voters remain committed to their president, which is quite the conundrum for a Democratic party debating how to bounce back in 2020.

In previous elections, the Democrats have sought the help of social psychologist Robert Cialdini. A professor at Arizona State University who pioneered the study of persuasion, Cialdini was part of a team of behavioural scientists that helped propel Obama to victory in 2012. He was also consulted in the early stages of Hillary Clinton’s campaign, though, he points out, he was much less involved in that race. Clinton’s major disadvantage, he believes, was that she was a continuity candidate in a change election.

“I would have advised her to say Obama’s policies have been brilliant but the state of the country is different now ... and we’re going to accommodate our policies to the new state of affairs,” he says. “That would have allowed her to be a change candidate in a change election.”

Were the Democrats to seek his advice this time, Cialdini would tell them to resist blaming the president’s supporters. “[Trump voters] don’t want to believe that they were stupid,” he says. “Cognitive dissonance research shows that the more consequential your error, the less willing you are to believe it was an error, because that undercuts your view of yourself as a good decision maker.”

Reassuring Trump voters that the consequences of their actions couldn’t have been predicted and allowing them to save face is the more persuasive approach – and he sees a parallel with the Brexit vote. “The bigger the mess, the less people want to believe they’re responsible for it, so they don’t register it as an error.”

Cialdini popularised the theory of social proof, which maintains that people will often look to their peers to decide what to think and how to behave. His book, Influence, published in 1984 and one of the best-selling books on behavioural psychology, was followed by a sequel two years ago, Pre-suasion, in which he explains the ideal conditions for exerting influence.

Cialdini’s principles of persuasion have long been applied to marketing and business management. Successfully winning people over, in every field from politics to the workplace, he says, can come down to the right word in the right place. If you are presenting an idea at work and you want to get your team on side, whatever you do, don’t ask for their opinion on it, Cialdini says. “When we ask someone for an opinion that person takes a half step back from us and becomes a critic.” Instead of using the word opinion, you should ask for advice on your plan. “That person takes a half step forward because the word ‘advice’ asks for their collaboration.”

‘Trump would often say: “Turn your TV cameras round, look at all of these people who are here.”’ Photograph: Julie Dermansky/Corbis via Getty Images

HMRC also uses psychological insights to influence behaviour. The government’s behavioural insights team, or “nudge unit”, added a line to tax letters sent to the public saying that the majority of UK citizens pay their taxes on time, which it claimed raised an extra £210m in payments. Cialdini says his UK-based consultancy, Influence At Work, advised HMRC to put that line in.

A similar use of the social proof principle was on display in Obama’s 2012 campaign. The venues Obama spoke at were vast, and instead of flags and banners, he had people behind him on the podium. In this way, he explains, Obama was able to validate his legitimacy as a candidate and make observers think: “If a lot of people have decided this guy is worthy of their support, then he’s at least worthy of my attention.” Trump took this pioneering tactic to another level.

“At the beginning of his speech, Trump would often say ‘Turn your TV cameras round, look at all of these people who are here’, so he specifically established the size of the crowd and the enthusiasm for him as a candidate before he began the speech.”

Trump also presented himself as someone who had conquered the world of business to establish himself as an authority figure, another persuasive tactic. This approach is something the Democrats could now turn to their advantage if they characterise Trump’s view of the US government as a company he owns and can do what he wants with, Cialdini believes. “I think most people would have a negative reaction to that.”

There is an argument that deploying psychological insights to change behaviour can amount to influence by stealth or manipulation. But Cialdini believes that the ethics of persuasion should only be called into question if the information presented in order to gain influence is false.

“If the evidence is accurate then not only is it ethically acceptable, it’s ethically commendable that we inform people into choices that sit with the existing information or evidence on the topic,” he says.

Ultimately, anyone seeking to be more influential should never underestimate the value of being nice to people. Paying someone a genuine compliment gets them on side, Cialdini advises. “People will want to work with those they feel a sense of rapport with, and are much more willing to give grace to those leaders with whom they feel an emotional connection. Praise where praise is warranted.”

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